<< but just keep in mind that NURBS solids are not really designed to be made up of many thousands of little faceted
Sure but how make when you must have a nurbs file as result ?
Tsplines ? (I kow they are free in free Fusion 360 but fusion don't love a such file...or Max Smirnov ? ;)

<< the reason that you need this as nurbs?

The problem was that the molder company has only nurbs format for their material folding engine!
(and even they don't know what was an "OBJ" format! The real world is sometime very astonished)

the other is that the OBJ original was not verified as welded edges! But I discovered that during the process!

So my complete order was

Decimate the original OBJ something like (250 000 --> 50 000) Meshlab (free) or Decimate Master (Zbrush not free)
so it's the new original decimated for all workflows following!

for me that was evident that the edges were welded so i even not verify that! :)

- Import inside Moi (thx Max Smirnov)
- SudDivision inside Moi (thx Max Smirnov)
- Unsuccess of the result - not of the subdivision - due the edges not welded (facettes separared and rounding very cool effect but...)
so...new workflow
- Inside Moi Import Original / Export original as OBJ with welded Edges (Thx Max & Michael)
- New session of Moi
- Inside Moi import this new OBJ "welded"
- SudDivision inside Moi (thx Max Smirnov)
- Success (Head takes less 5 minutes! 5 000 surfaces)
I suppose that for the entiere figurine you must decimate more ! Seems maxi for _subdiv_beta9 is 8 000 faces !
- Export as Step or IEGS (Thx Michael) (formats wanted by the Molder company)

Sorry I can't give the original OBJ but it was a very common file as you can find on the web!
(but verify the weld states of edges! :)

@Marco
I will study your workflow : quadface can of course an advantage! Seems a very cool prog for make quads! :)
(i have also in Zbrush but want not use it for have the same that the third person who will use the max of free program)

About your "reverse engineering" that is very cool but don't forget that I must also make the more simple
for somebody who know nothing about 3D! It's for that i took a relatively big file! 50 000 faces ;)

PS i precise that I made that for a third person who don't know anything about 3D world!
and I had not real contacts: only advises, and teach workflow possible! :)
So he discovers with great pleasure Moi! ;)
I have not yet final real result in metal or other material! :)